New York City is sinking by up to four millimetres a year under the weight of all its skyscrapers. The United States Geological Survey calculated New York has around 1,080,000 buildings. They weigh around 764 billion kilograms. There is additional weight from furniture, the transport infrastructure, and the weight of the city's 8.5 million inhabitants. Dr Tom Parsons said the gradual sinking and rising sea levels could make New York prone to natural disasters. He said new high-rise buildings could increase flood risks, especially along coasts and rivers.

The researchers compared New York City to Venice and Jakarta. Venice is experiencing more floods despite its new $5.3 billion system of sea walls. Indonesia is building a new capital city from scratch because Jakarta is sinking. The United Nations forecast that 70 per cent of the world's population will live in cities by 2050. Dr Parsons said: "When you build a city and it gets full of people, you end up with subsidence." He said New York was typical of a place where many people move to and then has a high concentration of new buildings.